Reading pacer



A. J. sPARLlNG READING FACER Nov. 3, 196.4

2 Sheets-Sheet 1 Filed July 30. 1962 INVENTOA 'ITHUR J JPARL/NG BY rmqwfy A. J. 'sPARLlNG Nov. 3, 1964 READING FACER 2 Sheets-Sheet 2 Filed July 30, 1962 United States Patent O 3,155,381 REAENG PACER Arthar .lodean Sperling, 6.38 14th St.,

Manhattan Beach, Calif. Fiied duly 3?, 1962, Ser. No. 213,410 12 Claims. {CL 267--1) This invention relates to timers adapted for timing operations such as reading pacing, and has as its general object to provide a timer embodying means for transmitting linear movement at a uniform rate to a pointer or indicator nger operable for scanning the lines of a printed page at a selected uniform rate, or for other equivalent indication function.

The invention aims particularly to provide a relatively simple and inexpensive timing mechanism for transmitting movement at a uniform rate which may be varied within selected limits. More specifically it is an object to provide a timer having a relatively simple adjustment for varying the rate of timer movement and manually controllable as by the rotation of a knob.

The further object is to provide a timer of indefinitely long life, havin Y only a few extremely simple and inexpensive wearing parts and subject to being easily serviced for replacement of such parts when worn.

Toward the attainment of the foregoing objects, the invention'contemplates a timer utilizing air pressure differential, acting against a restricted orifice bleed for delayed escape of hydraulic fluid from a dashpot chamber, for controlling the rate of linear timing movement which is transmitted from an air pressure differential responsive part to an indicator part. More specifically, the invention provides, in a hydraulic timer, a movement rate-controlling oriiice and a needle valve which is operable to vary the area of the orifice and thus vary the rate of timing movement.

A further object is to provide such a timer in which timing movement is effected by energy ina form of an air pressure dhiferential, stored by the simple operation of forcibly extending (drawing apart) the two component assemblies of a pneumatic actuator.

A further object is to provide such a timer wherein timing movement is effected by the controlled bleed of hydraulic liquid from one chamber to another. Another object is to provide such a timer wherein a timing bleed is bypassed in the setting operation, relatively unrestricted bypass ports being provided for bypass of the hydraulic fluid evacuated from a storage chamber of the apparatus; and wherein such unrestricted ports are blocked off from the path ofreentry of the hydraulic liuid into the storage chamber so as to require all return ilow to pass the restricted bleed. p

Toward the attainment of the foregoing objects, the invention contemplates a timer utilizing air pressure differential acting against a piston to develop a force and consequent motion. The piston couples via a rod to a second piston in a hydraulic dashpot chamber wherein the movement rate is controlled by means of controlled liuid flow past a restricted orifice bleed.

Other objects and advantages of the invention will become apparent in the ensuing specifications and accompanyin g drawings, in which:

FG. 1 is a plan view of a reading pacer embodying my invention;

FIG. 2 is a fragmentary longitudinal sectional view of the same, viewed from the same direction as FIG. l, the parts being shown in closed relationship as attained at the end of a timing stroke;

FIG. 3 is a fragmentary axial sectional View of the same timing stroke is commenced;

3,155,381 Patented Nov. 3, 1964 FIG. `i is a fragmentary detail sectional view of parts of the timer on an enlarged scale; v

FlG. 5 is a transverse sectional view taken on the 1in 5 5 of FIG. 2;

FIG. 6 is a transverse sectional view taken on the line 6--6 of FIG. 2;

FlG. 7 is a transverse sectional view taken on the line 7 -7 of FIG. 2. i

General Description of Invention .Referring now to the drawings in detail, I have shown therein, as an example of one form in which the invention may be embodied, a reading pacer comprising, in general, an outer cylinder unit A; an inward cylinder unit B which is axially slidable in said outer cylinder unit A; a piston unit C iixedly attached to the outer cylinder A and slidable within the inward cylinder unit B; a needle valve assembly D which controls a bleed orifice in the inward cylinder unit E; and an indicator assembly E attached to the inward cylinder unit B and adapted to indicate movement of the unit B with respect to the outer cylinder unit A (when the latter is held in a fixed position).

A vacuum chamber F (FIG. 3) is dened between respective heads of inward and outer cylinder units B and A at the closed end of assembly A, whereby when the units A and B are drawn apart, the atmospheric pressure, acting against the closed ends of the two cylinder units, will be operative to draw the units together into closed relationship shown in FIG. 2. ln the closed condition of the timer, the chamber F is reduced to substantially zero volume, in the form of a flat annular plane of contact between adjacent heads of the respective units A and B as indicated F in FIG. 2. In order to Valleviate the need for such close fitting, it is contemplated that a low vapor pressure oil or grease may be added in small quantity toll any unavoidable recesses or tolerance gaps thus to make more positive the exclusion of all air. Thus the outer and inner cylinder units cooperatively constitute a pneumatic actuator which is powered by the differential between the atmospheric pressure of air acting externally thereon and the substantial vacuum existing in chamber F internally thereof.

Timing controi is provided by a dashpot action cooperatively exercised by the inward cylinder unit B and the piston unit C, in which hydraulic liuid is discharged from a dashpot chamber G through a bleed orifice regulated by the valve assembly D, into a storage chamber H. The unique operation of the timer is particularly characterized by this combination of the action of stored energy in the form of adifferential of atmospheric pressure over a substantial vacuum in chamber F, acting against the resistance of hydraulic liquid which is expelled at a controlled rate from dashpot chamber G so as to effect the closing of the cylinder units upon one another with a uniform-rate linear movement.

Detailed Description Outer cylinder A comprises a unit cylinder 15 pneumatically closed at its outer end by a head 16 which preferably has a flange 17 engaging the end of cylinder 1S. The head 16 is pneumatically sealed in the cylinder 15, preferably by a press-fit or if desired, by a suitable adhesive or by brazing or sweating its cylindrical external surface to the internal surface of cylinder 1S. At its opposite end, cylinder 15 is provided with a collar 18, one side of which has a cylindrical guide bearing 19. Collar 18 snugly encircles the cylinder 15 and is suitably secured thereto.

Secured in an axial bore in the head 16 is one end of a stem Z1 by means of which the piston unit C is fixedly attached to the head 16.

A bearing bushing 22 of tough, smooth, wear-resistant material such as T eflon is secured to the inner wall of cylinder at its open end to provide a bearing surface in which the cylinder of unit B is freely slidable.

Inward cylinder unit B comprises a middle cylinder 26 which is closed at its inner end by a head comprising a cup seal 27 of soft, flexible, tough, wear-resistant material Such as Teflon mounted upon a cylindrical tubular portion 28 of a seal support embodying an intermediate shoulder 29 in the form of a fiat ring, and having a cylindrical skirt portion 30. Cup seal 27 has a liexible rim 31 surrounding an annular air space 32 between the cup seal 27 and the shoulder 29. Rim 31 is adapted to expand into tight sealing engagement with the inner wall of outer cylinder 15 in response to a differential in pressure of air in annular space 32 over that of vacuum chamber F as the inward cylinder unit B is moved away from the outer cylinder head 16. Skirt 3f) has an annular groove adjacent to shoulder 29, into which the end of middle cylinder 26 is contracted at 33 to secure the cylinder to the seal support 28-30.

Secured in the outer end of middle cylinder 26 is an internally threaded nut 35 having ta head 36 which functions to secure an annular index plate 37 against the end of cylinder 26. Secured between the inner end of nut 35 and seal support 28-3@ is a series of annular parts including a middle cylinder head 3S having "a cylindrical valve seat body 39 at its inner end; an inner cylinder 4t) telescoped over the valve seat body 39 at one end, and a cap 41 receiving the other end of inner cylinder 4t), the cap 41 and middle cylinder head 38 being engaged within the respective ends of a thin tubular membrane 42 and being fitted within the middle cylinder 26 with the ends of said membrane interposed and sealed to the inner wall of the middle cylinder 26. At one end, the membrane 42 is clamped between the outer end of middle cylinder head 38 and the inner end of nut 35. At its other end, membrane 42 is clamped between the contracted end 33 of cylinder 26 and the skirt 30 of the seal support 28-30. The end cap 41 is abutted against a reduced end portion of skirt 30, which reduced end portion is spaced radially inwardly from the middle cylinder 26 to define an annular space in which an 'O-ring 45 is compressed between the skirt and the cylinder and against the end cap 41 to pneumatically seal the membrane 42 to the seal support 28-30. The support is sealed to rod 21 by an O-ring 46 and a seal collar 47 jointly nested within a counterbore in the support 28-30, the collar 47 having a thin tubular tip 48 which is contracted into snug sealing engagement with the piston stem 21 by the expansive force of compressed 0-ring 46. Collar 47 is of wear resistant, tough flexible plastic material such as Teflon, while the IC rings 45 and 46 are of medium soft elastic material such as soft rubber or equivalent.

Middle cylinder head 38 has an external annular groove which receives an O-ring 49 that is compressed between the bottom of the groove and the inner surface of membrane 42, backed by the wall of middle cylinder 26.

Value seat body 39 has a small diameter axial bleed orice (bore) 50 which at its forward end communicates with dashpot chamber G and, at its rear end, intersects the flat rear wall of body 39 to define a needle Valve seat 51. Orifice 50 communicates with a valve chamber 52 which is defined between said rear wall and a forward extremity of needle valve assembly D. Valve seat body 39 is joined integrally to middle cylinder head 38 by a thin cylindrical waist section 53 which has a plurality of radial transfer ports 54 communicating the valve chamber 52 with an annular transfer passage 55. Passage 55 is defined between the inner cylinder 4t) and the body of membrane 42 which is disposed in the annular cylindrical space defined between the cylinders 26 and 40, the respective ends of this space being closed by the rim portion of end cap 41 and the portion of middle cylinder head 33 which projects radially outwardly from the reduced waist portion 53 thereof. The membrane 42 is free to expand and contract within this annular space, with a breathing action so as to vary the volume of transfer passage 55 in accordance with fluid displacement requirements as will be explained more fully hereinafter. A corresponding breathing action, through the wall of middle cylinder 26, to accommodate variations in the volume of the air space defined between membrane 42 and the middle cylinder 26, is provided for by vents 56 in the cylinder 2d. Vents 56 are located near the end of middle cylinder 26 so that they are never exposed to the user even when the middle and outer cylinders are fully extended. Thus, said breathing action through vent holes 56 as mentioned and hence along the annular passage between middle cylinder 26 and outer cylinder 15. Where this annular passage is restricted by bearing support ring 22 provision is made for air passage by making the ring 22 discontinuous (a split ring) with a slot therein functioning as an air passage. Within the inner cylinder 40, around the stem 21, is defined the hydraulic fiuid storage chamber H, which communicates with the transfer passage 55 adjacent the end cap 41 through return ports 5S in the inner cylinder 40, whereby, as hydraulic uid is forced through bleed orifice 5t) by piston assembly C during the closing movement of inward cylinder unit B into outer cylinder unit A, such hydraulic fluid can pass freely from valve chamber 52 through unrestricted ports 54 into transfer passage 55, traveling the length thereof and entering the storage chamber 57 through return ports 53. In the outer end of cylinder 26 are one or more vents 59 for the purpose of breathmg.

Piston assembly C comprises a stem 21 and a piston 61 secured and sealed to the free end thereof. The body of piston 61 is of smaller diameter than the internal diameter` of inner cylinder 40, and is spaced from the latter by an annular bypass passage 62. At its free end, piston 61 has a head 63 in the form of a radial liange, which is joined to the body of the piston by a reduced tubular neck 64. The neck 64 is spaced radially inwardly from the inner wall of inner cylinder 40 to define an annular ring groove in which a valve ring 65 is axially slidable. In the reduced neck 64 are a plurality of radial bypass ports 66 adapted to be loosely covered by the valve ring 65 and, when uncovered, establishing communication between the bypass 62 'and a central axial chamber 67 defined within the neck 64. When the valve ring 65 is in the closed position shown in FIG. 2, it seats against a valve seat provided by a radial annular shoulder 59 on piston 61, to establish a hydraulic seal. Valve ring 65 is sealed to the inner wall of inner cylinder 4t? and engages the same with a frictional engagement having a differential over that of its engagement with the reduced neck 64, sufficient to cause the valve ring 65 to be automatically shifted between its alternate positions as the result of the drag against the cylinder 49 at the commencement of each piston stroke (each time the movement of inner cylinder assembly B is reversed with respect to the outer cylinder and piston assemblies). Thus, in setting the timer (by drawing the two cylinder assemblies apart) the leftward movement of inner cylinder 40, as seen in FIG. 2, with respect to the stationary piston 61, will drag the valve ring 65 to the position shown in FIG. 3, uncovering the bypass ports 66 so that hydraulic fluid may freely flow from the storage chamber H around the piston 61 in the bypass passage 62, through the ports 66 into the central axial chamber 67 and thence into the dashpot chamber G with which the chamber 67 is in open communication. Thus the dashpot chamber G will be filled with hydraulic fluid as the cylinder assemblies A and B are drawn apart. Part of the fluid filling chamber G will flow through ports 54 from annular passage 55 in conjunction with the collapsing of the membrane associated with compensating the volume change attendant the extraction of piston rod stem 21. The opening movement of valve ring 65 occurs at the beginning of the operation of extending the cylinder units, and is limited by engagement of the valve ring 65 against piston head flange 63 as shown in FIG. 3.

In the begining stage of timing operation, the return movement of cylinder unit B into outer cylinder unit A drags the valve ring 65 from the open position of FIG. 3 back to the closed position of FIG. 2, thus blocking return flow of hydraulic liquid through annular bypass passage 62 and directing the full return flow through the restricted bleed orifice Sil, with the result that the closing movement of the inner cylinder unit is a delayed one, occuring slowly at at timed rate regulated by the needle valve assembly D which will shortly be described.

Y The closing movement of valve ring 65 is limited by engagement against the annular shoulder defined at the outer end of the body portion of piston 6l. This shoulder, and the head flange 63, define the respective sides of the annular valve chamber in which the val 1e ring o5 is shiftable.

Needle valve assembly D comprises a screw '71 threaded into the nut 35; a knob 72 on the outer end of screw 71, for manual actuation thereof, the knob being secured to the screw in any suitable manner, as by the integral bridging neck 73; a cylindrical shank 74 extending inwardly from the inner end of screw 71 as a coaxial integral extension thereof; an O-ring seal 7S mounted in an annular groove in the shank 74 and sealing the same to the cylindrical bore of sleeve 38, in which the shank 74- is rotatably fitted; and a needle valve 7o press-fitted in an axial bore in shank '74, extending into bleed passage Sti and cooperating with valve seat 51 to regulate the effective area of the passage 5t), thus regulating the timing rate of the timer. The annular space within nut 3'3" and around the shank 7d is vented to atmosphere through a slot 77 extending axially through the peripheral areas of knob 72 and screw 71.

Rotation of knob 72 to advance and retract the needle valve 7e will correspondingly restrict and enlarge the bleed passage 50 so as to respectively lengthen and shorten the timing period of operation.

Indicator assembly E comprises a rod 3G one end of which is secured in an ear Si formed as an integral radial projection on index plate T17; and an indicator finger S2 which is secured to the other end of rod Si) as by means of an integral sleeve 332 wrapped around a reduced tip S4 of rod Sd. The indicator nger 32 has sufiicient width to cover a number of lines of reading matter and, for lightweight construction, can be fabricated of ribbon metal or stiff plastic.

Rod 84B is slidably guided in the cylindrical guide bearing 19 as the inner and outer cylinder units A and B are extended in telescoping movements of the inner assembly B with respect to the outer assembly A. A stop collar 85 (FIGS. 1 and 3) is secured to rod Si) adjacent the linger S2. Collar 85 abuts the guide bearing 31 in the fully extended position of inner asssembly B, thus determining the limit of extension thereof.

A number of aspects of operation, set forth in detail in the foregoing description, will be referred to more riefly in the ensuing explanation in which these various aspects of operation are correlated.

Where the timer is used in pacing the reading of a printed page, it may be arranged in a vertical position with its leftward end, as seen in FIG. l, disposed at the top, and its rightward end provided with suitable clips or other fasteners for attaching it to the support for the page being read. To commence the use of the timer, the respective cylinder units A and B are grasped in the hands of the user and pulled apart so as to set the timer in a starting position such as is shown in FiG. 1. If this is done with the timer detached from its holder, the outer end of cylinder assembly A is then attached to the holder with the line guide indicator ringer S2 extending over the top of the printed page. The subsequent closing movement of cylinder unit B into unit A will move the line guide finger S2 downwardly over the page so as to successively cover succeeding lines of printed matter at a timed rate determined by the setting of needle valve 72.

As the cylinder units A and B are drawn apart, the v chamber F, which has substantially Zero volume at the closed position shown at F' in FIG. 2, is opened to full volume, but since it is hermetically sealed due to the fact that the rightward end of outer cylinder l5 is sealed by head 16 and the inward end of inner cylinder unit B is sealed to the inner wall of cylinder l5 by the resilient cup seal 27, no air or other fluid will be permitted to enter the chamber F, and a substantial vacuum will be generated therein as the inner cylinder unit B is drawn out of the outer unit A. Thus energy in the form of atmospheric pressure exerted against the outer ends of the respective cylinder units, is stored in the timer and is effective to return the inner cylinder unit B to a closed position when released for such movement.

During the opening movement, the piston unit C, iixed to the outer cylinder head lo by stem 21, remains in a fixed position while the valve head 39 of the inner cylinder unit B is moved away from it, thus expanding the dashpot chamber G from minimum volume in the closed condition as shown in FIG. 2 to maximum volume in the extended condition of the timer, and correspondingly reducing the volume of storage chamber H, between piston unit C and the inner end cap 41 of inner cylinder 49, from maximum volume in the closed condition as shown in PIG. 2. Thus, with suction being developed in dashpot chamber G as it is expanded with compression being developed in storage chamber H as it is contracted, the hydraulic liquid contained in storage chamber H will be placed under compression and, since it cannot freely flow through annular transfer passage 55 and past needle Valve 76 and restricted orifice Si), most of the liquid will be forced through annular bypass passage 62 around piston 6l, moving the valve ring 6' from its closed position of FG. 2 to its open position of FIG. 3 (with the assistance of frictional engagement of the valve ring 65 by the inner cylinder 4t) as it is extended). y The hydraulic fiuid will then be bypassed from the contracting storage chamber H into the expanding dashpot chamber G through bypass passage 62, ports do and chamber 67.

At this point it should be noted that although the outer diameters of chambers H and G are the same, the cross sectional area of chamber H is reduced by that of stem 21 while there is no corresponding reduction of the cross sectional area of chamber G. Consequently, the increase in volume in chamber G will not match the decrease in volume in chamber H, for any increment of axial shifting movement of the inner cylinder unit B, but will occur at a faster rate than the decrease in volume in chamber H. Accordingly, as hydraulic fluid is transferred from chamber H to chamber G, reserve fluid will be drawn from transfer passage 55 through port 58 into chamber` H to balance the difference in the volume increase in chamber G over the volume decrease in chamber H.

The withdrawal of reserve fluid from transfer passage 55 will be accompanied by an inward breathing contraction of membrane 42 and a corresponding breathing flow of air through ports 56 into the annular space around membrane 42 within middle cylinder 25.v

After the cylinder units A and B have been extended and released for closing movement, air pressure acting against the outer ends thereof will yieldingly press them together, being sealed olf from the vacuum chamber F by the seals 27, 16 at the outer end of unit A and by seal 27 sealing between outer cylinder 15 and end member 28, and by seals 46, 47 and 4S sealing between end piece 2S and stern 21, and by seals 49, 75 and membrane 42, sealed between valve sleeve 3d and middle cylinder 26, at the outer end of unit B. As the closing movement commences, Valve ring will be dragged from its open position of FIG. 3 to its closed position of FG. 2, sealing olf the annular bypass 62 against return movement of iuid around piston 61V and forcing the hydraulic fluid to dissuesser 7 charge through bleed orifice 50 as the volume of dashpot chamber G is gradually reduced. Passing the needle valve seat l, the iluid will enter the valve chamber 52, from which it will exit through escape ports 54 into the annular transfer passage 55 from which it will pass through return ports 5S back into the storage chamber H. ln this return flow, the increase in volume in storage chamber H will be less than the decrease in volume in dashpot chamber G, with an excess of fluid being gradually retained in transfer passage 55, with a corresponding expansion of membrane 42 to accommodate such excess, and with a corresponding outward breathing of air from the space outwardly f membrane 42. through the breather ports 56. The rate of return flow is regulated by the needle valve 76, and a uniform rate, slow, timed movement of line guide finger 82, transmitted to it from timer unit B, will result.

l claim:

l 1. A timer comprising, in combination: an outer head pneumatically closing one end thereof; a middle cylinder having a head which substantially abuts said outer head in the closed relation of said cylinders and which is separated therefrom in the extended relation of said cylinders, to define a vacuum chamber between said heads within said outer cylinder; means on said middle cylinder head pneumatically sealing the same to the inner wall of said outer cylinder to maintain a vacuum in said chamber; an inner cylinder mounted in a fixed position within said middle cylinder; means defining a transfer passage extending longitudinally between said inner and middle cylinders; a piston disposed within said inner cylinder, said piston having a stem extending through and sealed in said middle cylinder head and secured to said outer and thus in a fixed position relative to the outer cylinder, storage and dashpot chambers being defined within said inner cylinder at respective ends of said piston; a body of hydraulic fluid disposed in said storage and dashpot chambers; means, including a restricted bleed orifice and said transfer passage, providing a path for delayed discharge of hydraulic fluid from said dashpot chamber upon relative closing movements of said cylinders in response to atmospheric pressure against the outer ends of said cylinders; means providing relatively free bypass flow of hydraulic uid from said storage chamber into said dashpot chamber in response to relative extension of said outer and middle cylinders; manually adjustable means for varying the effective area of said restricted bleed orifice so as to regulate the rate of timing movement of said middle cylinder into said outer cylinder; and a valve ring encircling said piston, axially slidable thereon, and in sliding engagement with the inner wall of said inner cylinder, said piston having bypass passage means for bypass flow of hydraulic fluid from said storage chamber past said piston within said inner cylinder to said dashpot chamber, said bypass passage means being closed by said `Jalve ring during timing movement of said inner cylinder, whereby to block bypass flow and to force the hydraulic fluid to escape through said restricted bleed orifice at a relatively slow, timed rate.

2. A timer comprising, in combination: an outer cylinder having an outer head pneumatically closing one end thereof; a middle cylinder having a head which substantially abuts said outer head in the closed relation of said cylinders and which is separated therefrom in the extended relation of said cylinders, to define a vacuum chamber between said heads within said outer cylinder; means on said middle cylinder head pneumatically sealing the same to the inner wall of said outer cylinder to maintain a Vacuum in said chamber; an inner cylinder mounted in a xed position within said middle cylinder Iand in radially inwardly Ispaced relation thereto so that an annular space is defined between said inner and middle cylinders; a piston disposed within said inner cylinder, said piston having a stem extending through and sealed in said middle cylinder head, traversing said storage chamber axially, and secured to said outer head and thus in a fixed position relative to the outer cylinder, storage and dashpot chambers being defined within said inner cylinder at respective ends of said piston, said inner cylinder having a return port communicating said annular space and said storage chamber; a body of hydraulic iuid disposed in said storage and dashpot chambers; means, including said annular space, said return port and a restricted bleed orifice providing a path for delayed discharge lof hydraulic iiuid from said dashpot chamber upon relative closing movements of said cylinders in response to atmospheric pressure against the outer ends of said cylinders; and means providing relatively =free bypass flow of hydraulic iiuid from said storage chamber past said piston into said dashpot chamber in response to extending movement of said outer and middle cylinders.

3. A timer as defined in claim 2, including a tubular membrane surrounding said inner cylinder within said annular space, said membrane being sealed to the respective ends or" said inner cylinder and defining therewith an annular transfer passage communicating at one end with `the discharge end of said restricted bleed orifice, said return port providing communication between said transfer passage and said storage chamber at the end of said inner cylinder remote from said restricted bleed orifice, said membrane having a breathing action to compensate for a differential between the respective increments of volume change in said dfashpot chamber and said storage chamber resulting from reduction in net volume of said storage chamber by the presence of said stem therein, as one of the chambers is increased while the other is decreased in volume during relative movement between said outer and middle cylinders.

4. in a timer, in combination: an outer cylinder having an outer head sealing one end thereof; a middle cylinder slidably telescoped in said outer cylinder and having a head sealed in said outer cylinder, substantially closed against said outer head when said cylinders are in closed relation to yone another, and separated from said outer head when said cylinders are extended so as to define within said outer cylinder between said heads a vacuum chamber providing for a differential of atmospheric pressure acting externally against said cylinders over -a substantial vacuum within said chamber, thus providing stored energy for effecting closing movements of said cylinders with respect to one another after they have been pulled apart; dashpot mechanism including an inner cylinder fixed within said middle cylinder and spaced radially inwardly therefrom, means sealing one end of said inner cylinder to said middle cylinder adjacent said middle cylinder head, tan inner cylinder head sealing the other end of `said inner cylinder to said middle cylinder, said inner cylinder head having a valve body provided with an axially extending restricted bleed orifice, a piston within said inner cylinder having a stem extending through said middle cylinder head and secured to said outer head, a storage chamber being defined around said stem within said inner cylinder at one end of said piston and a dashpot chamber being defined between the other end of said piston and said valve body, a tubular membrane disposed in an annular space which is defined between said inner and middle cylinders, sealed at its respective ends to said inner cylinder, a variable volume transfer passage being detined between said membrane and the outer wall of said inner cylinder, said inner cylinder head having a port providing communication between said bleed orifice and one end of said transfer passage, said inner cylinder having a return port providing communication between the other end of said transfer passage and said storage chamber, said membrane having a breathing action to vary the volume of said transfer passage to compensate for a differential between the rates of volume change in said dashpot chamber and storage chamber respectively as one of said chambers expands while the other contracts, said piston including a body portion spaced radially inwardly fiom the inner Wall of said inner cylinder to deiine an annular bypass passage around said piston and having an annular ring groove communicating with the end of said bypass passage nearest said dashpot chamber, having a radial bypass pont communicating with said ring groove and an axial chamber communicating said radial port with said dashpot chamber, and a valve ring seated in said ring groove and axially slidable therein between a position closing said bypass passage during contraction of said dashpot chamber whereby to restrict the escape of said hydraulic duid from said dashpot chamber to slow bleed through said bleed orifice, and shiftable to an alternate position uncovering said bypass passage when said storage chamber is contracting, whereby to provide for relatively unrestrioted bypass flow from said st rage chamber -to said annular bypass passage around said piston, thence through said radial bypass port and said axial piston chamber into said dashpot chamber.

5. In a timer, in combination: an outer cylinder having an outer head sealing one end thereof; a middle cylinder slidably telescoped in said outer cylinder and having a head sealed in said outer cylinder, substantially closed against said outer head when said cylinders are in closed relation to one another, and separated from said outer head when said cylinders are extended so as to deiine within said outer cylinder between said heads a vacuum chamber providing for a differential of atmospheric pressure acting externally against said cylinders over a substantial vuum within said chamber, thus providing stored energy for effecting closing movements of said cylinders with respect to one and another after they havel been pulled apart; dashpot mechanism including an inner cylinder fixed within said middle cylinder and spaced radially inwardly therefrom, means sealing one end of said inner cylinder to said middle cylinder adiacent said middle cylinder head, an inner cylinder head sealing the other end of said inner cylinder to said middle cylinder, said inner cylinder head having za valve body provided with an axially extending restricted bleed orifice, a piston within said inner cylinder having a stern extending through said middle cylinder head and secured to said outer head, a storage chamber being defined around said stem within said inner cylinder at one end of said piston and a dashpot chamber being defined between the other end of said piston and said valve body, a tubular membrane disposed in an annular space which is defined between said inner and middle cylinders, sealed at its respective ends to said inner cylinder, a variable volume transfer passage being defined between said membrane and the outer wall of said inner cylinder, said inner cylinder head having a port providing communication between said bleed orifice and one end of said transfer passage, said inner cylinder having a return port providing communication between the other end of said transfer passage and said storage chamber, said membrane having a breathing action to vary the volume olf said transfer passage to compensate for a differential between `the rates of volume change in said dashpot chamber und storage chamber respectively as one of said chambers expands while the other contracts, said piston including a body portion spaced radially inwardly from the inner wall of said inner cylinder to dene an annular bypass passage around said piston and having an annular ring groove communicating with the end of said bypass passage nearest said dashpot chamber, having a radial bypass port communicating with said ring groove and an axial chamber communicating said radial port with said dashpot chamber, and a valve ring seated in said ring groove and axially slidable therein between a position closing said bypass passage during contraction of said dashpot chamber whereby to restrict the escape of said hydraulic fluid from said dashpot chamber to slow bleed through said bleed orifice, and shiftable to an alternate position uncovering said bypass passage when said :storage chamber is contracting, whereby to provide for relatively unrestricted bypass flow from said storage chamber to said annular bypass passage around said piston, thence through said radial bypass port and said axial piston chamber into said dashpot chamber, said inner cylinder head comprising a sleeve extending from one end of said valve body :toward the outer end of said middle cylinder, a needle valve having a cylindrical shank journalled within said sleeve and provided with an annular external groove, an O-ring seal disposed in said external gnoove and sealing said shank to the inner wall of said valve sleeve, an internally threaded nut mounted in the outer end of said middle cylinder in end-to-end relation to said sleeve, ,a screw secured to and projecting outwardly from said needle valve shank and threaded into said nut for axial advancement and retraction of said needle valve upon rotation thereof, and a lmob on the outer end of said screw for manual engagement to effect such rotation.

6. A timer as dened in claim 4, including a needle valve mounted in said inner cylinder head and extending into the outlet end of said restricted bleed orifice to vary the effective :area thereof ,whereby to regulate the period of timing operation of said timer.

7. ln a timer, in combination: an outer cylinder having an outer head sealing one end thereof; a middle cylinder slidably telescoped in said outer cylinder and having a head sealed in said outer cylinder, substantially closed against said outer head when said cylinders are in closed relation to one another, and separated from said outer head when said cylinders are extended so as to define within said outer cylinder between said heads a vacuum chamber providing for a differential of atmospheric pressure acting externally against said cylinders over substantial vacuum within said chamber, thus providing stored energy for effecting closing movements of said cylinders with respect to one and another after they have been pulled apart; dashpot mechanism including an inner cyli. der xed within said middle cylinder and spaced radially inwardly therefrom, means sealing one end of said inner cylinder to said middle cylinder adjacent said middle cylinder head, an inner cylinder head sealing the other end of said inner cylinder to said middle cylinder, said inner cylinder head having a valve body provided with a restricted bleed orifice, a piston within said inner cylinder having a stem extending through said middle cylinder head and secured to said outer head, a storage chamber bein g defined around said stem within said inner cylinder at one end of said piston and a dashpot chamber being defined between the other end of said piston and said Valve body, in communication with said restricted bleed orifice, a tubular membrane disposed between said inner and middle cylinders, sealed at its respective ends to said inner cylinder head and to said one end of said inner cylinder, a variable volume transfer passage being defined between said membrane and the outer wall of said inner' cylinder, said inner cylinder head having a port providing communication between said valve chamber and one end of said transfer passage, said inner cylinder having a return port providing communication between the other end of said transfer passage and said storage chamber, said membrane having a breathing action to vary the volume of said transfer passage to compensate for a differential between the rates of volume change in saidv dashpot chamber and storage chamber respectively as one of said chambers expands while the other contracts, said piston including a body portion spaced radially inwardly from the inner Wall of said inner cyclinder to define an annular bypass passage around said piston and having a bypass post communicating with said bypass passage and with said dashpot chamber, and valve means on said piston, shiftable to a position closing said bypass port during contraction of said dashpot chamber whereby to restrict the escape of said hydraulic liuid from said dashpot chamber l l. y

to slow bleed through said bleed oriiice, and shiftable to an alternate position uncovering said bypass port when said storage chamber is contracting, whereby to provide for relatively unrestricted bypass ow from said storage chamber to said annular bypass passage around said piston, thence through said radial bypass port and said axial piston chamber into said dashpot chamber.

8. A timer as deiined in claim 7 including an indicator rod having a free end secured to the outer end of the middle cylinder and extending in external parallel relationship to the outer cylinder; and an indicator element carried by the free end of said indicator rod and indicating relative movement between the outer and middle cylinders.

9. A timer as defined in claim 8 including a guide yoke secured to the inner end of the outer cylinder and having a bearing in which said indicator rod is slidably engaged and guided.

10. A timer as defined in claim 7 including a thinwalled bearing bushing of tough, wear-resistant plastic material secured to the inner wall of said outer cylinder adjacent its inner end, said middle cylinder having slidable bearing engagement within said bushing.

11. A timer as defined in claim 7, wherein said middle cylinder head has a skirt portion anchored within an adjacent end of said middle cylinder, wherein one end of said tubular membrane is interposed between said skirt portion and said adjacent end of the middle cylinder to provide the sealed connection between the one end of said membrane and the adjacent end of said inner cylinder, and wherein the other end of said tubular mem` brane is engaged between said inner cylinder head and 12 the inner wall of said middle cylinder to provide the sealed connection between the other end of said membrane and the other end of said middle cylinder.

12. A timer as dened in claim 7, wherein said middle cylinder head has a skirt portion anchored within an adjacent end of said middle cylinder, wherein one end of said tubular membrane is interposed between said skirt portion and said adjacent end of the middle cylinder to provide the sealed connection between the one end of said membrane and the adjacent end of said inner cylinder, and wherein the other end of said tubular membrane is engaged between said inner cylinder head and the inner wall of said middle cylinder to provide the sealed connection between the other end of said membrane and the other end of said middle cylinder, and including an Oring seal disposed in an annular groove in said skirt portion of the middle cylinder head and sealed within the one end of said tubular diaphragm, a sealing collar disposed in an annular recess within said skirt portion around said piston stern, said collar having a thin liexible tip projecting from one side thereof, and a resilient O-ring disposed between said tip and the inner wall of said skirt portion and yieldingly pressing said tip into sealing contact with said stem.

References Cited in the tile of this patent UNITED STATES PATENTS 2,108,881 Casper Feb. 22, 1938 2,351,397 Buchet June 13, 1944 2,531,368 Tack et al Nov. 21, 1950 2,551,347 Stephenson May l, 1951 2,925,670 French Feb. 23, 1960 

1. A TIMER COMPRISING, IN COMBINATION: AN OUTER HEAD PNEUMATICALLY CLOSING ONE END THEREOF; A MIDDLE CYLINDER HAVING A HEAD WHICH SUBSTANTIALLY ABUTS SAID OUTER HEAD IN THE CLOSED RELATION OF SAID CYLINDERS AND WHICH IS SEPARATED THEREFROM IN THE EXTENDED RELATION OF SAID CYLINDERS, TO DEFINE A VACUUM CHAMBER BETWEEN SAID HEADS WITHIN SAID OUTER CYLINDER; MEANS ON SAID MIDDLE CYLINDER HEAD PNEUMATICALLY SEALING THE SAME TO THE INNER WALL OF SAID OUTER CYLINDER TO MAINTAIN A VACUUM IN SAID CHAMBER; AN INNER CYLINDER MOUNTED IN A FIXED POSITION WITHIN SAID MIDDLE CYLINDER; MEANS DEFINING A TRANSFER PASSAGE EXTENDING LONGITUDINALLY BETWEEN SAID INNER AND MIDDLE CYLINDERS; A PISTON DISPOSED WITHIN SAID INNER CYLINDER, SAID PISTON HAVING A STEM EXTENDING THROUGH AND SEALED IN SAID MIDDLE CYLINDER HEAD AND SECURED TO SAID OUTER HEAD AND THUS IN A FIXED POSITION RELATIVE TO THE OUTER CYLINDER, STORAGE AND DASHPOT CHAMBERS BEING DEFINED WITHIN SAID INNER CYLINDER AT RESPECTIVE ENDS OF SAID PISTON; A BODY OF HYDRAULIC FLUID DISPOSED IN SAID STORAGE AND DASHPOT CHAMBERS; MEANS, INCLUDING A RESTRICTED BLEED ORIFICE AND SAID TRANSFER PASSAGE, PROVIDING A PATH FOR DELAYED DISCHARGE OF HYDRAULIC FLUID FROM SAID DASHPOT CHAMBER UPON RELATIVE CLOSING MOVEMENTS OF SAID CYLINDERS IN RESPONSE TO ATMOSPHERIC PRESSURE AGAINST THE OUTER ENDS OF SAID CYLINDERS; MEANS PROVIDING RELATIVELY FREE BYPASS FLOW OF HYDRAULIC FLUID FROM SAID STORAGE CHAMBER INTO SAID DASHPOT CHAMBER IN RESPONSE TO RELATIVE EXTENSION OF SAID OUTER AND MIDDLE CYLINDERS; MANUALLY ADJUSTABLE MEANS FOR VARYING THE EFFECTIVE AREA OF SAID RESTRICTED BLEED ORIFICE SO AS TO REGULATE THE RATE OF TIMING MOVEMENT OF SAID MIDDLE CYLINDER INTO SAID OUTER CYLINDER; AND A VALVE RING ENCIRCLING SAID PISTON, AXIALLY SLIDABLE THEREON, AND IN SLIDING ENGAGEMENT WITH THE INNER WALL OF SAID INNER CYLINDER, SAID PISTON HAVING BYPASS PASSAGE MEANS FOR BYPASS FLOW OF HYDRAULIC FLUID FROM SAID STORAGE CHAMBER PAST SAID PISTON WITHIN SAID INNER CYLINDER TO SAID DASHPOT CHAMBER, SAID BYPASS PASSAGE MEANS BEING CLOSED BY SAID VALVE RING DURING TIMING MOVEMENT OF SAID INNER CYLINDER, WHEREBY TO BLOCK BYPASS FLOW AND TO FORCE THE HYDRAULIC FLUID TO ESCAPE THROUGH SAID RESTRICTED BLEED ORIFICE AT A RELATIVELY SLOW, TIMED RATE. 